Uniaxially-aligned sulfonated polyimide (SPI) nanofibers fabricated by an electrospinning method showed ultra-high proton conductivities above 1 S cm−1 at 30–90 °C and 95% RH. Higher applied voltage between the parallel electrodes during the electrospinning process gave higher proton conductive SPI nanofibers due to the formation of an effective proton conduction pathway by molecular orientation in the nanofibers.
